The reapers have returned from dark space. With Earth under attack and the mass relays in a state of chaos from refugees and the councils fleet engaging reaper forces the galaxy is a mess. The outcome is unknown, the warfare is devastating. The galaxy will never be the same.

Maybe a support type frigate/cruiser that disrupts the ability usage of the enemy, maybe recharge rate or temp disable their weapon systems? The Asari seem the type to have support ships that buff your allies, shield/hull repair, range buffs among others. Also this looks like a perfect fit for the Salarians.

That's why I suggest they have abilities like increased weapon range for a limited time. Since there GARDIAN systems and laser cannons use a lot more power then normal weapons so sustained fire would difficult.
Also A stealth dreadnought would be an awesome addition to the council forces.

Well as they are a council race the codex says they have dreadnoughts as well, as many as the treaty will allow for at least. In ME3 it mentions that they had actually managed to outfit a full size dreadnought with stealth systems like the Normandy had, allowing it to maneuver for favorable firing positions undetected.